The invention relates to an apparatus for ultrasonic processing of workpieces comprising a converter plate, at least one feed unit mounted on the converter plate, at least one vibratory structure coupled to said feed unit and having a converter, a sonotrode and a longitudinal axis, and means for adjusting the vibratory structure in at least two directions running transversely to its longitudinal axis.
Known apparatuses of this type (e.g. DE 4 206 584 C2) are used in particular for joining two workpieces by spot, rivet, stud or surface welding, wherein at least one of the two workpieces consists of a thermoplastic material. The workpieces are heated locally strongly enough to melt together. The heating of the workpieces is effected in that a sonotrode excited to vibrate mechanically is pressed against at least one of the workpieces by means of a feed unit, wherein the sonotrode is a component of a vibrating structure which is mounted on the feed unit and comprises the sonotrode, a converter and optionally an amplitude transformation piece interposed between these two. In processing only one workpiece these vibrations can also be used to shape or cut the workpiece. Since sonotrodes vibrate as a rule at ultrasonic frequencies of 20 kHz or 35 kHz for example, such processing operations are generally referred to as ultrasonic processing. The main field of use of the described apparatuses lies in the processing of plastics parts, which are used to house electrical devices and to a special degree in the automobile industry, both for body parts such as bumpers and also for interior linings, such as door linings and consoles. The sonotrodes in contact with the workpiece are designed variously, depending on the nature and material of the workpieces to be processed.
Welds of the described kind are for example carried out in that the sonotrode is pressed against selected points or on a so-called weld or rivet pin of the workpiece, which is formed on a first workpiece lying on an anvil, projects through a corresponding hole of a second workpiece to be attached to the first workpiece and is for example 10 mm high and optionally of hollow cylindrical form. Of importance to the quality of a weld effected in this or another way or of other processing is inter alia the precision with which the sonotrode is placed on the processing site in question. If workpieces with only one processing site are involved, it is comparatively simple to bring the sonotrode into the right position. However it is always a problem when workpieces of the kind referred to above are involved, which have a plurality of processing sites to be processed at the same time.
In such cases it is usual to mount all necessary sonotrodes or their feed units on a common component, called a converter plate, which is arranged stationary at a place on the welding machine or the like located above the workpiece to be processed. The positioning of the feed units on this converter plate is effected in the factory of the manufacturer on the basis of data which is supplied by the user of the machine. The machine manufacturer provides the converter plate with the bores calculated from the received data, which serve to receive the fixing screws passing through the feed units, and installs the finished and bored converter plate in the machine or possibly in a tool change assembly. If it is found after installing the vibratory structures that not all of the numerous sonotrodes reach the processing sites provided for them, expensive re-finishing operations are necessary, since the feed units in question, including the vibratory structures fixed to them, have to be dismounted. Further, the converter plate has to be provided with fresh bores using hand drilling machines, and the feed units must then be fixed on the adapter plate again.
As well as this it is already known U.S. Pat. No. 5,976,314 to provide selected feed units with a mounting body on which a plurality of vibratory structures are fixed in common and to provide means in the form of slots and fixing screws passing through the slots for adjusting the positions of the vibratory structures on the mounting body. However, such adjusting devices only serve for adjustable fixing of the sonotrodes on the mounting bodies and can in any case only serve for relative adjustment of the positions of the sonotrodes on the common mounting body. If the mounting body itself is mounted incorrectly on the adapter plate, the position of the mounting body on the adapter plate has first to be corrected, before the adjustment of the relative positions of the sonotrodes can be begun. In addition, also with likewise already known constructions which comprise means for altering the positions of the sonotrodes within the vibratory structures, alterations of the fixing points of the feed units on the adapter plates are frequently unavoidable. Accordingly the difficulties in accurate positioning of the feed units on the adapter plate are not obviated by such adjusting devices.
On the basis of the above, it is an object of the invention to so design the apparatus of the kind initially specified that an inaccurate positioning of the feed units in the first mounting does not require the expensive refining operations mentioned above.
A further object of the invention is to design the apparatus specified above such that positional inaccuracies of the sonotrodes in the first mounting can be dealt with by comparatively simple means.
Yet another object of the invention is to design the apparatus specified above such that positional inaccuracies of the sonotrodes in the first mounting can be dealt with even subsequently and after mounting the converter plate on a welding machine or the like.
These and other objects which will become apparent hereinafter are solved, briefly stated, with an apparatus having a converter plate comprising a plurality of fixing means, said, fixing means being arranged in a manner of a raster and such that said at least one feed unit can be mounted on the converter plate with the aid of at least one fixing means selected from the plurality of fixing means.
The invention provides the advantage that the converter plate formed as a raster plate already has been provided in the factory with said fixing means, which can serve for mounting the feed units. Accordingly, if a feed unit is positioned incorrectly, because of faulty data or because of any kind of error in the factory of the welding machine manufacturer or the like, attempts can be made firstly to correct the error with the aid of the existing adjusting means. If this does not suffice, the feed unit only needs to be fixed to the convener plate with the aid of another fig means, without new calculations, bores or the like having to be carried out.
Further advantageous features of the invention appear from the dependent claims.
The invention will be explained in more detail below in conjunction with the accompanying drawings of embodiments.